You might consider getting your hands dirty on this one.
With the power shut off, open the case. Relocate the cards inside the computer to new slots - mix them all up. Close the case and power the computer back up. Immediately get into BIOS.
Go into the PNP settings on the motherboard and enable the ESCD update (if available), save, and reboot. This should force the motherboard to rebuild the PNP hardware table it reports to Windows.
Once Windows starts, it should find new hardware all over the place, and hopefully should end the conflicts. If not, let's hear what devices you have, where they are currently (IRQ-wise), and which ones are showing conflicts. Frequently the less expensive sound cards will take up resources all over the place that you don't need, and have alternate setups that can be used that don't eat as many. If your modem is conflicting with a serial port, move the modem to Com2, and set Com2 on the motherboard to load as Com3 or disable it entirely (do this in BIOS). Particularly with a serial mouse in Com1, a modem on Com3 will go totally braindead (or hose the mouse) when you try using the two devices, as they share IRQ4. By moving the modem to Com2, you change its IRQ to 3.
Another source of conflicts for many people is onboard equipment conflicting with aftermarket add-on equipment. I've actually worked on machines that had built-in sound cards and the customer added their own Sound Blaster and couldn't figure out why the onboard sound didn't just magically go away. Same thing with MANY video cards.
(whoever decided to put those things onboard should be SHOT)
Regardless, if you do it right, you should be able to get all of your equipment running without conflicts, provided it's not an IBM Stinkpad like the one sitting on my desk
